This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present technological advancement. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present technological advancement. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
A subsea production system utilizing any combination of equipment (trees, manifolds, jumpers, flow lines or pipelines, etc.) produces hydrocarbon sales fluids (oil or gas) from a subsea well or a plurality of wells. Non-sales fluids (primarily water, but may also include sand fines) are produced along with the sales fluids. A report on worldwide nominal water and oil production showed for every barrel of oil approximately four barrels of water are produced. The produced water may be transported to the host via production flow line with the oil or gas, or costly disposal wells are required to dispose of the produced water (as shown as FIGS. 1A and 1B). For either option, significant CAPEX is involved for topside equipment or subsea injection wells. The OPEX can be high too due to the need of mitigate produced water induced corrosion or solid induced erosion.
FIG. 1A depicts host facility 101 extending above the water line 102, with umbilical 103 (including hydraulic cables and hoses for chemical injection), power umbilical 104, production flow line 105, and gas export flow line 106. Umbilical 103 ends at umbilical termination assembly (UTA) 106, which then connects to subsea distribution units (SDUs) 107, in order to provide hydraulic power and/or chemicals to water injection manifold 108 (a subsea structure containing a network of valves and pipework designed to direct injection fluids to one or more subsea wells) and production manifold 109 (a subsea structure containing valves and pipework designed to commingle and direct produced fluids from multiple wells into one or more flow lines) via trees 110 (an assembly of valves, spools, pressure gauges, and chokes to control production or hydrocarbons or injection of water) that are connected to production manifold 109. The water injection manifold 108 can be connected to subsea water injection treatment (SWIT) system 111, which can include subsea chemical storage, and can obviate the need for an umbilical to supply chemicals. Power umbilical 104 can be connected to an UTA 106 and a transformer 112 to provide power for subsea production, injection or processing operations. The production line 105 can be routed from the production manifold 109 to the host via a high integrity pressure protection system (HIPPS) 115, separator system 114, and pump station 119. Gas export flow line 106 can be routed from the separator system via flow line termination (FLET) 116 to the host. The separator system 114 can separate water from production fluids and supply the water to the water injection manifold, for injection into water disposal wells 117. However, they system of FIG. 1A could alternatively have a water flow line back to host 101.
FIG. 1B shows a remote development scenario such as offshore arctic. Here the umbilical 103, power umbilical 104, production flow line 105, and gas export flow line 106 tied are to an onshore facility 117. A gas compression station 118 downstream of separator system 114 will likely be needed to boost gas pressure for transportation to the onshore facility 117. Gas compression station 118 can include a dehydration system.
While this document describes the discharge of non-sales fluids at the seabed, this is not necessarily a current industry practice. Furthermore, implementation of such discharge may require compliance with regulations governing produced water disposal and discharge of sand, and such regulations could prohibit such discharge in certain regions of the world.